As far as everyone is aware, Runouw is too busy working on Last Legacy and won't be updating Super Mario 63 any time soon (if ever again).
Anyways if you want "NPCs" that the player can talk to, you should
disable the thing you want the player to talk to then place a sign nearby with your dialogue.
If you really want scripts that trigger when you enter a specific area, SM63 cannot do that. However both
Last Legacy and
Last Legacy: Null Space are capable of doing that and a whole lot more with event triggers.
Under Renovations. . .